With FlashCut CNC Version 5.0 and 6.0, you simply change the mechanism type in the Configuration...Machine...Drive Parameters Menu then Choose Drive Mechanism fir the axis you wan to edit.
With FlashCut CNC Version 4.0, you simply change the mechanism type in the Configuration...Machine...Drive Parameters Menu.
For older version, use the equation below to find the Screw Thread equivalent for your Rack and Pinion drive mechanism:
Screw Thread = Rack teeth per unit length / Pinion Teeth
For example, if you have a 20 tooth pinion and a rack with 5 teeth per inch, you would find your mechanism's "screw thread" to be 0.25 (screw rev/inch). In the Mechanics Settings portion of the Configuration Menu, enter the value that you found using the above equation for the Screw Thread field of that mechanism.
If you have a gear train or pulley between the pinion and your drive motor, put the pulley ratio of this mechanism into the Gear Ratio field. For example, if your motor has a 10 tooth pulley that drives a 20 tooth pulley using a belt, the Gear Ratio would be 2 (motor rev/screw rev).
For other types of drive mechanisms, enter the number of motor turns per unit length traveled by the axis.